Isoelectric Focusing of Long-Acting Thyroid Stimulator Immunoglobulin G

Lonergan, C.; Babiarz, D.; Burke, Gerald

doi:10.1210/jcem-36-3-439

Cited by 12 publications

(5 citation statements)

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“…Graves' IgGs on isoelectric focusing was between pH 8.0 and 9.5, which is in agreement with earlier studies on LATS (Smith, 1971;Adlkofer et al, 1973;Lonergan et al, 1973) and thyroid slice adenylate cyclase activity (Zakarija et al, 1978). The isoelectric distribution of receptor binding was similar to that of thyroid stimulating activity in four Graves' IgGs, although in two of these, the relative amounts in different fractions varied.…”

Section: Discussionsupporting

confidence: 90%

IgG THYROTROPHIN RECEPTOR ANTIBODY ACTIVITY IN GRAVES' DISEASE; A STUDY OF TSH AGONIST AND ANTAGONIST ACTIVITIES BY ISOELECTRIC FOCUSING

Creagh

Howells

Williams

et al. 1986

Clinical Endocrinology

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The distribution of TSH receptor antibody activity in the 7S and 19S fractions of Graves' sera has been re-evaluated. Serum fractions were obtained by gel filtration from 12 Graves' sera and assayed for TSH receptor binding activity in a radioreceptor assay. Thyroid stimulating activity was determined in a cultured porcine thyroid cell bioassay. In apparent contrast to the findings of Baker et al. (1983) TSH receptor binding activity was confined to the 7S gel filtration fraction, containing IgG, and was not detected in the 19S fraction, containing IgM. Similarly thyroid stimulating activity was detected only in the 7S fraction. 7S fractions from seven Graves' sera were fractionated by isoelectric focusing and the fractions analysed for TSH receptor binding activity and TSH agonist and antagonist activities. Five of the IgGs showed TSH agonist activity and in all five, the peak thyroid stimulating activity (measured by stimulation of cyclic AMP release from isolated porcine thyroid cells) was in fractions with a pI of between 8.0 and 9.5. In four of these five IgGs, TSH receptor binding activity showed similar isoelectric distribution to the thyroid stimulating activities. High levels of TSH receptor binding activity without associated TSH agonist or antagonist activity were however observed in some isoelectric fractions of the fifth stimulating Graves' IgG studied. All the isoelectric fractions from the fifth IgG with thyroid stimulating activities contained TSH receptor binding activity. Two of the Graves' IgGs showed TSH antagonist activity and both the TSH receptor binding and TSH antagonist activities of these IgGs showed similar isoelectric distribution with the peak activities at a pI of around 9.0. Consequently, it was not possible to separate TSH agonist or TSH antagonist activities from TSH receptor binding activity in seven Graves' sera by isoelectric focusing although in one IgG several isoelectric fractions contained isolated receptor binding activity. These findings are in keeping with the hypothesis that the biological activities of Graves' IgGs are intimately related to their ability to bind to the TSH receptor.

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Section: Discussionsupporting

confidence: 90%

IgG THYROTROPHIN RECEPTOR ANTIBODY ACTIVITY IN GRAVES' DISEASE; A STUDY OF TSH AGONIST AND ANTAGONIST ACTIVITIES BY ISOELECTRIC FOCUSING

Creagh

Howells

Williams

et al. 1986

Clinical Endocrinology

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“…A similarly alkaline fraction of normal IgG was also the most effective in the TBI assay. On the other hand, the pH of the optimally effective thyroidstimulating fraction was 8.5-9.0, as described previously from this laboratory (32) and by others (1,12).…”

Section: Discussionmentioning

confidence: 80%

The Thyroid-Stimulating Antibody of Graves’ Disease: Evidence for Restricted Heterogeneity

Zakarija¹

1980

Horm Res

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The thyroid-stimulating antibody (TSAb) of Graves’ disease was shown to have a relatively constant pH on preparative isoelectric focusing; the fraction of pH 8.5–9.0 was maximal in thyroid-stimulating potency but inhibition of thyrotropin-binding (another property of Graves’ disease IgG) was most marked with pH 9.5–10.6 fraction. H and L chains of TSAb-IgG were separated and H original (Ho) was combined with L original (Lo) and with Bence Jones L_k and Lλ. Only H_O + L_O restored (minimal) bioactivity. Of isolated TSAb-IgGĸ and TSAb-IgGλ only IgGλ was thyroid stimulating. Sub-classes (IgG3 and IgG 1 + 2+4) of TSAb-IgG were prepared and with all of 6 sera TSAb was in IgG 1 + 2+4 with none in IgG3. These data combine to suggest restricted heterogeneity of this autoimmune antibody.

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“…Consequently, separation of the two activities on the basis of molecular size is not feasible. However, serum IgG can be fractionated by isoelectric focusing and the distribution of TRAb in the various fractions analyzed (47)(48)(49)(50)(51). Creagh et al (51) attempted to separate blocking and stimulating activity in seven different Graves' IgGs by isoelectric focusing but were unsuccessful.…”

Section: Attempts To Separate Blocking and Stimulating Antibodies mentioning

confidence: 99%

“…Several studies have shown that the isoelectric point (pi) of TRAb is in the region of 8-10 irrespective of whether the antibodies act as TSH agonists or antagonists (47)(48)(49)(50)(51)111). Furthermore, the pi of TSH is about 9 (111).…”

Section: Charge-charge Interactions and The Tsh Receptormentioning

confidence: 99%

Autoantibodies to the Thyrotropin Receptor

1988

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This review considers recent developments in our understanding of the properties of TRAb, particularly measurement of the antibodies and their sites of action and synthesis. Two new assay methods have allowed considerable improvements in the sensitivity, specificity, precision, and ease of measuring TRAb. In particular: 1) receptor assays based on inhibition of receptor-purified labeled TSH binding to detergent-solubilized TSH receptors and 2) bioassays based on stimulation of cAMP release from monolayer cultures of isolated thyroid cells. Detailed studies with the two assays indicate that TSH receptor antibodies nearly always act as TSH agonists in patients with a history of Graves' hyperthyroidism. Studies in areas of dietary iodine sufficiency suggest that measurement of the antibodies at various stages in the course of treating Graves' disease can be of value in predicting the outcome of therapy. However, in areas of iodine deficiency, difficulties in the ability of patients' thyroid tissue to recover from the effects of antithyroid drugs may prevent the receptor antibodies from causing a relapse of thyrotoxicosis. Consequently, the predictive value of receptor antibody measurements would be expected to be lower in these geographical areas. Although patients with a history of Graves' hyperthyroidism nearly always have TRAb which act as TSH agonists, about 20% of patients with frank hypothyroidism due to autoimmune destruction of the thyroid have TRAb which act as TSH antagonists (blocking antibodies). There is some evidence that these blocking antibodies can cause hypothyroidism particularly in the neonate. With regard to the site of synthesis of TRAb, there is now direct evidence that they are synthesized by thyroid lymphocytes, particularly the lymphocytes in close proximity to thyroid follicular cells. This is consistent with the well established effects of antithyroid treatment (drugs, radioiodine, or surgery) on TRAb levels in addition to their effects on thyroid hormone synthesis. Recent studies using affinity labeling with 125I-labeled TSH have enabled elucidation of the structure of the TSH receptor. TSH receptors in human, porcine, and guinea pig thyroid tissue have a two-chain structure in which the TSH binding site is formed on the outside surface of the cell membrane by a water-soluble A subunit (Mr approximately 50 K). The A subunit is linked by a disulfide bridge and weak noncovalent bonds to the amphiphilic B subunit (Mr approximately 30 K). This subunit, which penetrates the lipid bilayer, probably forms the site for interaction of the receptor with the regulatory subunits of adenylate cyclase.(ABSTRACT TRUNCATED AT 400 WORDS)

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Isoelectric Focusing of Long-Acting Thyroid Stimulator Immunoglobulin G

Cited by 12 publications

References 0 publications

IgG THYROTROPHIN RECEPTOR ANTIBODY ACTIVITY IN GRAVES' DISEASE; A STUDY OF TSH AGONIST AND ANTAGONIST ACTIVITIES BY ISOELECTRIC FOCUSING

IgG THYROTROPHIN RECEPTOR ANTIBODY ACTIVITY IN GRAVES' DISEASE; A STUDY OF TSH AGONIST AND ANTAGONIST ACTIVITIES BY ISOELECTRIC FOCUSING

The Thyroid-Stimulating Antibody of Graves’ Disease: Evidence for Restricted Heterogeneity

Autoantibodies to the Thyrotropin Receptor

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Isoelectric Focusing of Long-Acting Thyroid Stimulator Immunoglobulin G

Cited by 12 publications

References 0 publications

IgG THYROTROPHIN RECEPTOR ANTIBODY ACTIVITY IN GRAVES' DISEASE; A STUDY OF TSH AGONIST AND ANTAGONIST ACTIVITIES BY ISOELECTRIC FOCUSING

IgG THYROTROPHIN RECEPTOR ANTIBODY ACTIVITY IN GRAVES' DISEASE; A STUDY OF TSH AGONIST AND ANTAGONIST ACTIVITIES BY ISOELECTRIC FOCUSING

The Thyroid-Stimulating Antibody of Graves&rsquo; Disease: Evidence for Restricted Heterogeneity

Autoantibodies to the Thyrotropin Receptor

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The Thyroid-Stimulating Antibody of Graves’ Disease: Evidence for Restricted Heterogeneity